Two-thirds of Indians have antibodies shows ICMR survey

Subject: Science & tech

Context: The fourth national COVID-19 sero survey conducted by the Indian Council of Medical Research (ICMR).

Concept:

As per the sero-survey, two-thirds of the population aged above six have antibodies against SARS-CoV-2.
The survey also found that more than half of the children (6-17 years) were seropositive.
Though the survey offered a ray of hope in the fight against the pandemic, there was no room for complacency given that nearly 40 crore people, or a third of the population, are still vulnerable to the COVID-19 infection.

Serological survey

The serological survey was meant to detect whether the person being tested had developed antibodies against the coronavirus.
Since it is not possible to test everyone, detecting antibodies in random sets of people is an indirect way of estimating the extent of disease spread in a community.
The antibodies are proteins produced by the immune system to fight external organisms like viruses that try to enter the body.
These are produced only after the infection has happened, and are specific to the attacking virus or bacterium.
The presence of antibodies, therefore, is an indication that an infection by that particular virus or bacterium has already occurred.
Subsequent attempts to infect the body can be thwarted by these antibodies.

What about Vaccines then?

Vaccines work in a similar manner – wherein they inject harmless doses of a virus or a bacterium inside the human body to trigger the production of antibodies by the immune system.
These antibodies can then fight off an actual attack by those viruses or bacteria.

Herd Immunity

Herd immunity is a stage of an epidemic in which some members of a population group remain protected from infection because a majority of those around them have already developed immunity, either through vaccination or because they have been infected earlier.
Once a certain proportion of population gets infected, and thus builds immunity against the disease, the epidemic begins to slow down and eventually stop.
No one clearly knows what percentage of the population needs to be infected before herd immunity kicks in. It is different for different diseases, and different population groups.